Question

In Chrome, try the following in the console. First

console = 0;

to assign the value 0 to console. Then

console // (prints `0`)

to check we have correctly overwritten console. Finally,

delete console

Surprisingly, console now holds the original Console object. In effect, the delete keyword “resurected” console, instead of exterminating it!

Is this expected behaviour? Where is this implemented in the Chromium code?

Answer 1

As mentioned in MDN’s documentation on delete:

If the delete operator succeeds, it removes the property from the
object entirely, although this might reveal a similarly named property
on a prototype of the object.

Your delete simply unshadows native property inherited through prototype chain.

Some browsers have window inherit from native prototype and you’ll have check out sources to see how property is inherited, if you really want to know that much details, but mostly they work just like JS’ own.